1. Field of the Invention
The present invention relates to a data storage system and method of controlling the same, and, more particularly, to a method and apparatus to perform improved retry in a data storage system, which reduces a number of read retry attempts by making use of information regarding a previous successful retry.
2. Description of the Related Art
Related techniques are disclosed in Japanese Patent Publication Nos. 1999-066763 and 2000-067530.
Japanese Patent Publication No. 1999-66763 teaches a method in which information about a read retry position and corresponding read retry parameters are stored, and, after that, if a read retry should be attempted at the same position, the retry parameters are used to read data from the position. Japanese Patent Publication No. 2000-67530 teaches a method in which parameters of performed retries are sequentially stored with new parameters put on top, so that a fast retry can be achieved.
Generally, a hard disc drive is a type of data storage system that contributes to a system operation by reproducing data from a disc, or writing user data on the disc, using a magnetic head. Recently, in hard disc drives, there has been a trend toward high capacity, high density, and miniaturization. In particular, there has been a trend toward a high recording bit density in a rotating direction (bits per inch, BPI) and in a radial direction (tracks per inch, TPI). Thus, a more sophisticated mechanism to control the hard disc drive is needed.
As the mechanism or hardware feature to be applied to the hard disc drive is changed, errors may occur frequently while in the process of data reading. If errors occur in a reading/writing operation, a (read/write) retry process should be executed to successfully perform the reading/writing operation.
More specifically, when an error occurs during a reading operation, a read retry process is performed by varying values of parameters related to an off-track read or data read, and the retry process is repeated until it is successful or until a maximum number of retries is reached.
Generally, errors in reading tend to reoccur at the same location, and thus the probability of performing a retry process at such a location is high, which deteriorates the read function of a hard disc drive.